1. Field of the Invention
The present invention relates to a process for producing a light emitting device and more particularly, to a process for effectively producing a high performance semiconductor light emitting device.
2. Description of Prior Art
For most semiconductor devices such as a light emitting diode (LED), a laser diode, a photodetector and a transistor, an N-type doped layer and a P-type doped layer are often required. However, it is very difficult for doping high concentration P-type dopant in III-V or II-VI group of compound semiconductor materials. Typical examples are like: doping magnesium in III-V group of compound semiconductors such as InP, AlGaInP and AlGaInN; and doping magnesium in II-VI group of compound semiconductors such as ZnSSe.
One of the main reasons for the difficulty in forming P-type conductivity is the unintentional hydrogen incorporation and consequent acceptor passivation during an epitaxial growth process and a cooling process thereof. This will retard the P-type dopant in the semiconductor materials from meeting the requirement of high concentration.
Many attempts are provided to solve this problem, e.g. Antell et al. (Appl. Phys. Lett., 53, 1988, 758), Cole et al. (Electron. Lett., 24, 1988, 929), Hamada et al. (IEEE J. Quantum Electron., 27, 1991, 1483), Akasaki et al. (Japanese J. Appl. Phys. 28, 1989, L2112), and Nakamura et al. (U.S. Pat. No. 5,306,662). However, the problem is not solved to a desirable extent. Therefore, the applicant of the present invention discloses a microwaving process that can effectively solve the above problem in the U.S. application Ser. No. 09/497,316 (Method of Manufacturing Low Resistivity P-type Compound Semiconductor Material, taking the priority advantage of Taiwan Patent Application No. 89101337).
However, the microwave energy will activate the semiconductor device, especially for the N-type layer therein. A large quantity of the microwave energy will be absorbed by the N-type layer and propagates therein. The excess microwave energy will result in the cracking of the device. Therefore, the microwave energy and processing time should be strictly controlled so as to avoid product failure. This is inconvenient for production and may cause problems.
Aiming to this, the present invention provides a process that takes advantage of a microwaving process and avoids the shortcoming of cracking during the microwaving process as well.
An objective of the present invention is to provide a process for effectively producing high performance light emitting device. The present invention can avoid the shortcoming of device cracking during a microwaving process and maintain the integrity of the device. The quality of the light emitting device can be further ensured and the production yield be enhanced.
In a preferred embodiment, the present invention provides a process for producing a light emitting device. Firstly, a substrate is provided. On the substrate an N-type semiconductor layer, a light emitting layer, and a P-type semiconductor layer are sequentially formed. Next, one or more layers on the substrate are cut to a depth. And lastly, the substrate is microwaved. The way of cutting can be accomplished by etching, mechanical cutting, electrical cutting or laser cutting.
Preferably, the cutting depth substantially reaches the substrate, including on a top surface and to a partial depth thereof, or reaches a partial depth of the N-type semiconductor layer. The light emitting device is preferably a light emitting diode.
In another preferred embodiment, the present invention provides another process for producing a light emitting device. Firstly, a substrate is provided. On the substrate a P-type semiconductor layer, a light emitting layer, and an N-type semiconductor layer are sequentially formed. Next, at least a layer on the substrate is cut to a depth. And lastly, the substrate is microwaved.
Preferably, the cutting depth substantially reaches a partial depth of the N-type semiconductor layer, or substantially reaches a top surface of the light emitting layer, or substantially reaches the substrate.